avformat/swfdec: Do not error out on pixel format changes

Instead print an error and continue

Fixes Ticket4702
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/swfdec.c

@@ -407,10 +407,8 @@ static int swf_read_packet(AVFormatContext *s, AVPacket *pkt)
             }
             if (st->codec->pix_fmt != AV_PIX_FMT_NONE && st->codec->pix_fmt != pix_fmt) {
                 av_log(s, AV_LOG_ERROR, "pixel format change unsupported\n");
-                res = AVERROR_PATCHWELCOME;
-                goto bitmap_end;
-            }
-            st->codec->pix_fmt = pix_fmt;
+            }else
+                st->codec->pix_fmt = pix_fmt;
 
             if (linesize * height > pkt->size) {
                 res = AVERROR_INVALIDDATA;